It has been known that graft copolymers (AES resins) obtained by employing, as a base rubber component, EPM or EPDM that contains substantially no unsaturated bonds in the main chain thereof and by copolymerizing styrene, acrylonitrile or the like with the rubber component, are larger in resistance against ultraviolet light, oxygen and ozone, and markedly higher in weatherability than ABS resins that contain conjugated diene rubbers as the base rubber component. However, molded products conventionally obtained from AES resins are poor in appearance, and are sometimes unsatisfactory in physical properties at low temperatures. Accordingly, various improvements have been made; however, it has been difficult to improve molded products in appearance and low temperature properties better than the conventional levels since propylene is used as α-olefin in the rubber component.
Concurrently, there has been demanded an AES resin which is better in impact resistance than conventional AES resins. For the purpose of increasing the impact resistance, a method is conceivable in which content of the base rubber component in the products is increased, or a method in which molecular weight of rigid resin components (matrix components) is increased. However, the increase of the content of the base rubber component in the products is not preferable, because rigidity of the products is lowered, or appearance of the molded products is deteriorated. Additionally, with the method in which the molecular weight of rigid resin components is increased, fluidity is lowered, or appearance of the molded products is deteriorated. Thus, it has hitherto been difficult to improve the balance between the impact resistance and the other physical properties of products.
Although a method for improving molded products in appearance has been proposed in Japanese Patent Laid-Open (Kokai) No. H11-302339, further improvements are demanded in appearance at welded portions and such defects as flow marks and color unevenness at welded portions.